Technical Field
The present invention relates to a friction stir spot welding structure.
Related Art
Friction stir welding is known as a joining method in which a pair of panel members are joined together in a overlapped state (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2007-289976). Friction stir spot welding is also known as a similar type of joining method to friction stir welding.
In friction stir spot welding (FSSW or SFSW (spot friction stir welding)), first, the pair of mutually overlapped panel members are gripped by a clamp. Next, a rotating pin projecting out from a leading end of a tool is pressed, while rotating, against one panel member of the pair of panel members. A joint portion of the pair of panel members is softened by frictional heat accompanying the friction with the rotating pin, and the softened joint portion is stirred (plastic flow) by the rotating pin so as to become an integral unit.
There is a possibility of cracks, buckling, and the like occurring in the panel member if the panel member being pressed by the rotating pin follows the rotation of the rotating pin while this is being performed.